Detection of a leptin receptor variant and methods for regulating obesity

ABSTRACT

The present invention relates to a variant form of the receptor for the obese gene product. In particular, the invention relates to methods of detecting this receptor variant in cells and tissues of obese individuals. In addition, it relates to methods of inhibiting or down-regulating expression of this variant in cells to augment their responsiveness to weight regulation by leptin as well as methods of using compounds to directly activate signal transduction pathways associated with this ligand-receptor system.

The present application is a continuation-in-part of U.S. patent application Ser. No. 08/355,888, filed Dec. 14, 1994, now U.S. Pat. No. 5,763,211 which is a continuation-in-part of U.S. patent application Ser. No. 08/306,231, now U.S. Pat. No. 5,643,748 filed Sep. 14, 1994, each of which is incorporated by reference herein in its entirety.

TABLE OF CONTENTS

1. INTRODUCTION

2. BACKGROUND OF THE INVENTION

3. SUMMARY OF THE INVENTION

4. BRIEF DESCRIPTION OF THE DRAWINGS

5. DETAILED DESCRIPTION OF THE INVENTION

5.1. THE OB-R VARIANT

5.2. EXPRESSION OF THE OB-R VARIANT

5.3. USES OF THE OB-R VARIANT POLYNUCLEOTIDE

5.3.1. DIAGNOSTIC USES OF OB-R VARIANT POLYNUCLEOTIDE

5.3.2. THERAPEUTIC USES OF THE OB-R VARIANT POLYNUCLEOTIDE

5.4. ACTIVATION OF TYROSINE KINASE PATHWAYS IN OBESITY

6. EXAMPLE: MOLECULAR CLONING OF AN OB-R VARIANT

7. DEPOSIT OF MICROORGANISMS

1. INTRODUCTION

The present invention relates to a variant form of the receptor for the obese gene product. In particular, the invention relates to methods of detecting this receptor variant in cells and tissues of obese individuals. In addition, it relates to methods of inhibiting or down-regulating expression of this variant in cells to augment their responsiveness to weight regulation by leptin as well as methods of using compounds to directly activate signal transduction pathways associated with this ligand-receptor system.

2. BACKGROUND OF THE INVENTION

Obesity is not only a nutritional disorder in Western societies, it is also a serious health concern because of its association with adult-onset diabetes, hypertension, and heart disease (Grundy, 1990, Disease-a-Month 36:645-696). While there was evidence to suggest that body weight was physiologically regulated, the molecular mechanism has remained elusive. However, animal studies have produced several mouse strains that contain single-gene mutations, resulting in an obese phenotype. One such recessive mutation is manifested in the ob/ob mice, and it is referred to as the obese (ob) mutation.

Zhang et al. (1994, Nature 372:425-432) describe the cloning and sequencing of the mouse ob gene and its human homolog. When an isolated gene fragment was used as a probe, it was shown to hybridize with RNA only in white adipose tissue by northern blot analysis, but no expression was detected in any other tissue. In addition, the coding sequence of the ob gene hybridized to all vertebrate genomic DNAs tested, indicating a high level of conservation of this molecule among vertebrates. The deduced amino acid sequences are 84% identical between human and mouse, and both molecules contain features of secreted proteins.

In an effort to understand the physiologic function of the ob gene, several independent research groups produced recombinant ob gene product in bacteria for in vivo testing (Pelleymounter et al., 1995, Science 269:540-543; Halaas et al., 1995, Science 269:543-546; Campfield et al., 1995, Science 269:546-549). When the Ob protein (also known as leptin) was injected into grossly obese mice, which possessed two mutant copies of the ob gene, the mice exhibited a reduced appetite and began to lose weight. In addition, these studies described a dual action of leptin in both reducing the animals' food intake and in increasing their energy expenditure. Similarly, when normal mice received leptin, they also ate less than the untreated controls. More importantly, Campfield et al. (1995, Science 269:546-549) injected leptin directly into lateral ventricle, and observed a reduction in the animals' food intake, suggesting that leptin acts on central neuronal networks to regulate feeding behavior and energy balance. Thus, this result provides evidence that the leptin receptor (also known as OB-R) is expressed by cells in the brain.

Recently, a leptin fusion protein was generated and used to screen for OB-R in a cDNA expression library prepared from mouse choroid plexus, a tissue that lines brain cavities termed ventricles (Tartalia, 1995, Cell 83:1263-1271). This approach led to the cloning of one form of the OB-R coding sequence, which reveals a single membrane-spanning receptor, sharing structural similarities with several Class I cytokine receptors, such as the gp130 signal-transducing component of the interleukin-6 receptor (Taga et al., 1989, Cell 58:573-581), the granulocyte-colony stimulating factor receptor (Fukunaga et al., 1990, Cell 61:341-350), and the leukemia inhibitory factor receptor (Gearing et al., 1991, EMBO J. 10:2839-2848). Northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR) demonstrate that OB-R mRNA is expressed in several tissues, including lung, kidney, total brain, choroid plexus and hypothalamus.

The reported mouse OB-R protein contains a relatively short intracellular cytoplasmic domain as compared with other Class I cytokine receptors. Subsequently, when cDNA encoding its human homolog was isolated from a human infant brain library, the predicted human protein sequence contains a much longer intracellular domain. In view of this finding, it was speculated that different forms of the receptor might exist (Barinaga, 1996, Science 271:29). However, prior to the present invention, there was no report on the identification of any variant forms of the OB-R in humans or how such molecules, if they exist, would relate to obesity.

Additionally, several studies have shown that ob gene expression is actually increased in obese humans (Considine et al., 1995, J. Clin. Invest. 95:2986-2988; Lonnquist et al., 1995, Nature Med. 1:950; Hamilton et al., 1995, Nature Med. 1:953). Moreover, the mutations in the mouse Ob gene were not detected in human mRNA. Therefore, taken collectively, these studies imply that decreased leptin levels are not the primary cause of obesity, and argue for the presence of a less responsive receptor in obese individuals. There remains a need to isolate such an OB-R variant for the design of therapeutics to augment weight regulation by leptin.

3. SUMMARY OF THE INVENTION

The present invention relates to a variant form of the human OB-R. In particular, it relates to the detection of this receptor variant in cells of obese individuals, and methods for treating obesity by targeting this variant.

The invention is based, in part, upon the Applicants' discovery of human cDNA clones encoding a variant form of the OB-R. This receptor differs structurally from a reported OB-R with only three amino acid substitutions in the extracellular domain, but extensive diversity is observed in their intracellular cytoplasmic domains at the 3′ end. The cytoplasmic domain of the variant of the invention is both shorter and distinct in nucleotide sequence from the corresponding domain of the published form of OB-R. Therefore, a wide variety of uses are encompassed by the present invention, including but not limited to, the detection of the receptor variant in cells of obese individuals, methods to inhibit and/or down-regulate the expression of this receptor variant, gene therapy to replace the receptor variant in homozygous individuals, and direct activation of downstream signal transduction pathways in cells expressing the receptor variant for weight regulation.

4. BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1G. Nucleotide sequence and deduced amino acid sequence of the human OB-R variant. The amino acid sequence diverges from the human OB-R reported by Tartaglia et al. (1995, Cell 83:1263-1271) at nucleotide residue #349, #422, #764 and from residue #2770 and beyond.

5. DETAILED DESCRIPTION OF THE INVENTION 5.1. THE OB-R VARIANT

The present invention relates to nucleic acid and amino acid sequences of an OB-R variant in the Class I cytokine receptor family. In a specific embodiment by way of example in Section 6, infra, this variant was cloned and characterized. Amino acid sequence comparison of this OB-R variant with a published human OB-R sequence (Tartaglia et al., 1995, Cell 83:1263-1271) reveals three amino acid differences in their extracellular domain and extensive diversity in their intracellular cytoplasmic domains. More specifically, FIGS. 1A-1G show that in the variant, nucleotide residues #349-351 encode alanine, nucleotide residues #421-423 encode arginine and nucleotide residues #763-765 encode arginine. Additionally, the variant diverges both in length and sequence composition from the published human OB-R sequence from nucleotide residue #2770 and beyond.

In order to clone additional variant forms of the molecule, labeled DNA probes made from nucleic acid fragments corresponding to any portion of the cDNA disclosed herein may be used to screen a cDNA library prepared from human fetal liver, human lung, human kidney, human choroid plexus and human hypothalamus. More specifically, oligonucleotides corresponding to either the 5′ or 3′ terminus of the cDNA sequence may be used to obtain longer nucleotide sequences. Briefly, the library may be plated out to yield a maximum of 30,000 pfu for each 150 mm plate. Approximately 40 plates may be screened. The plates are incubated at 37° C. until the plaques reach a diameter of 0.25 mm or are just beginning to make contact with one another (3-8 hours). Nylon filters are placed onto the soft top agarose and after 60 seconds, the filters are peeled off and floated on a DNA denaturing solution consisting of 0.4N sodium hydroxide. The filters are then immersed in neutralizing solution consisting of 1M Tris HCL, pH 7.5, before being allowed to air dry. The filters are prehybridized in casein hybridization buffer containing 10% dextran sulfate, 0.5M NaCl, 50 mM Tris HCL, pH 7.5, 0.1% sodium pyrosphosphate, 1% casein, 1% SDS, and denatured salmon sperm DNA at 0.5 mg/ml for 6 hours at 60° C. The radiolabelled probe is then denatured by heating to 95° C. for 2 minutes and then added to the prehybridization solution containing the filters. The filters are hybridized at 60° C. for 16 hours. The filters are then washed in 1× wash mix (10× wash mix contains 3M NaCl, 0.6M Tris base, and 0.02M EDTA) twice for 5 minutes each at room temperature, then in 1× wash mix containing 1% SDS at 60° C. for 30 minutes, and finally in 0.3× wash mix containing 0.1% SDS at 60° C. for 30 minutes. The filters are then air dried and exposed to x-ray film for autoradiography. After developing, the film is aligned with the filters to select a positive plaque. If a single, isolated positive plaque cannot be obtained, the agar plug containing the plaques will be removed and placed in lambda dilution buffer containing 0.1M NaCl, 0.01M magnesium sulfate, 0.035M Tris HCl, pH 7.5, 0.01% gelatin. The phage may then be replated and rescreened to obtain single, well isolated positive plaques. Positive plaques may be isolated and the cDNA clones sequenced using primers based on the known cDNA sequence. This step may be repeated until a full length cDNA is obtained.

One method for identifying all 3′ isoforms is to PCR amplify the 3′ ends of the variant cDNA from a variety of tissues including but not limiting to, choroid plexus, hypothalamus, fetal liver, bone marrow, ovary, or prostate. To obtain the 3′ end of the cDNA, an oligo-dT primer is used to synthesize the cDNA first strand. OB-R specific primers from the conserved region of the gene (e.g. up stream of nucleotide 2770) and oligo-dT are then used to amplify the 3′ end. The PCR fragments are cloned and sequenced by standard techniques. Once obtained, these sequences may be translated into amino acid sequence and examined for certain landmarks such as continuous open reading frame, regulatory regions that associate with tyrosine kinase activation, and finally overall structural similarity to known OB-R variants.

5.2. EXPRESSION OF THE OB-R VARIANT

In accordance with the invention, the OB-R variant polynucleotide sequence which encodes a protein, peptide fragments, fusion proteins or functional equivalents thereof, may be used to generate recombinant DNA molecules that direct the expression of the protein, peptide fragments, fusion proteins or a functional equivalent thereof, in appropriate host cells. Such polynucleotide sequences, as well as other polynucleotides which selectively hybridize to at least a part of such polynucleotides or their complements, may also be used in nucleic acid hybridization assays, Southern and Northern blot analyses, etc.

Due to the inherent degeneracy of the genetic code, other DNA sequences which encode substantially the same or a functionally equivalent amino acid sequence, may be used in the practice of the invention for the expression of the OB-R variant. Such DNA sequences include those which are capable of hybridizing to the OB-R variant sequence under stringent conditions, particularly at its 3′ end. The phrase “stringent conditions” as used herein refers to those hybridizing conditions that (1) employ low ionic strength and high temperature for washing, for example, 0.015 M NaCl/0.0015 M sodium citrate/0.1% SDS at 50° C.; (2) employ during hybridization a denaturing agent such as formamide, for example, 50% (vol/vol) formamide with 0.1% bovine serum albumin/0.1% Ficoll/0.1% polyvinylpyrrolidone/50 mM sodium phosphate buffer at pH 6.5 with 750 mM NaCl, 75 mM sodium citrate at 42° C.; or (3) employ 50% formamide, 5×SSC (0.75 M NaCl, 0.075 M Sodium pyrophosphate, 5×Denhardt's solution, sonicated salmon sperm DNA (50 μg/ml), 0.1% SDS, and 10% dextran sulfate at 42° C., with washes at 42° C. in 0.2×SSC and 0.1% SDS.

Altered DNA sequences which may be used in accordance with the invention include deletions, additions or substitutions of different nucleotide residues resulting in a sequence that encodes the same or a functionally equivalent gene product. The gene product itself may contain deletions, additions or substitutions of amino acid residues within the OB-R variant sequence, which result in a silent change thus producing a functionally equivalent protein. Such amino acid substitutions may be made on the basis of similarity in polarity, charge, solubility, hydrophobicity, hydrophilicity, and/or the amphipathic nature of the residues involved. For example, negatively charged amino acids include aspartic acid and glutamic acid; positively charged amino acids include lysine, histidine and arginine; amino acids with uncharged polar head groups having similar hydrophilicity values include the following: glycine, asparagine, glutamine, serine, threonine, tyrosine; and amino acids with nonpolar head groups include alanine, valine, isoleucine, leucine, phenylalanine, proline, methionine, tryptophan.

The DNA sequence of the invention may be engineered in order to alter the OB-R variant coding sequence for a variety of ends, including but not limited to, alterations which modify processing and expression of the gene product. For example, mutations may be introduced using techniques which are well known in the art, e.g., site-directed mutagenesis, to insert new restriction sites, to alter glycosylation patterns, phosphorylation, etc. In addition, the intracellular domain may also be altered and replaced by a different domain, such as the OB-R intracellular domain by Tartaglia et al.

In another embodiment of the invention, the OB-R variant sequence may be ligated to a heterologous sequence to encode a fusion protein. For example, for screening of peptide libraries for inhibitors or stimulators of receptor activity, it may be useful to encode a chimeric protein expressing a heterologous epitope that is recognized by a commercially available antibody. A fusion protein may also be engineered to contain a cleavage site located between the OB-R variant sequence and the heterologous protein sequence, so that the variant may be cleaved away from the heterologous moiety.

In an alternate embodiment of the invention, the coding sequence of the OB-R variant could be synthesized in whole or in part, using chemical methods well known in the art. (See, for example, Caruthers et al., 1980, Nuc. Acids Res. Symp. Ser. 7:215-233; Crea and Horn, 180, Nuc. Acids Res. 9(10):2331; Matteucci and Caruthers, 1980, Tetrahedron Letters 21:719; and Chow and Kempe, 1981, Nuc. Acids Res. 9(12):2807-2817). Alternatively, the protein itself could be produced using chemical methods to synthesize OB-R variant amino acid sequence in whole or in part. For example, peptides can be synthesized by solid phase techniques, cleaved from the resin, and purified by preparative high performance liquid chromatography. (e.g., see Creighton, 1983, Proteins Structures And Molecular Principles, W.H. Freeman and Co., N.Y. pp. 50-60). The composition of the synthetic peptides may be confirmed by amino acid analysis or sequencing (e.g., the Edman degradation procedure; see Creighton, 1983, Proteins, Structures and Molecular Principles, W.H. Freeman and Co., N.Y., pp. 34-49).

In order to express the OB-R variant in host cells, the nucleotide sequence coding for the variant, or a functional equivalent, is inserted into an appropriate expression vector, i.e., a vector which contains the necessary elements for the transcription and translation of the inserted coding sequence. The expressed gene products as well as host cells or cell lines transfected or transformed with recombinant OB-R variant expression vectors can be used for a variety of purposes. For example, host cells expressing the OB-R variant may be used to verify the ability of this molecule to bind leptin in a binding assay with radiolabeled, enzyme-conjugated or fluorescent dye-conjugated leptin. At the same time, the ability of the molecule to transduce an activation signal in host cells upon binding to leptin may be tested by assaying proliferation or phosphorylation pattern of kinases in the cells. In addition, genetically-engineered host cells can be used to screen for and select agonist and antagonist compounds, including any inhibitors that would interfere with binding of leptin to the extracellular domain of the OB-R variant. In that connection, such host cells may be used to screen for and select small molecules that can supplement the incomplete signal transduced by the OB-R variant following leptin binding. Other uses, include, but are not limited to generating antibodies (i.e., monoclonal or polyclonal) that competitively inhibit activity of an OB-R variant, neutralize its activity, or even enhances it activity. Antibodies may be used in detecting and quantifying expression of OB-R levels in cells and tissues.

5.3. USES OF THE OB-R VARIANT POLYNUCLEOTIDE

The OB-R variant polynucleotide may be used for diagnostic and/or therapeutic purposes. For diagnostic purposes, the OB-R variant polynucleotide may be used to detect gene expression or aberrant gene expression in obese individuals as well as in normal individuals to identify predisposition for obesity. Included in the scope of the invention are oligonucleotide sequences, that include antisense RNA and DNA molecules, ribozymes and triplex DNA, that function to inhibit translation of OB-R variant.

5.3.1. DIAGNOSTIC USES OF OB-R VARIANT POLYNUCLEOTIDE

The OB-R variant polynucleotide may have a number of uses for the diagnosis of the possible causes underlying obesity, resulting from expression of the receptor variant. For example, the OB-R variant cytoplasmic domain DNA sequence may be used in hybridization assays of biopsies or autopsies to diagnose OB-R variant expression; e.g., Southern or Northern analysis, including in situ hybridization assays as well as PCR. Such techniques are well known in the art, and are in fact the basis of many commercially available diagnostic kits. For PCR detection, primers may be designed from a conserved region of the coding sequence and within the 3′ region of OB-R variant. The tissues suitable for such analysis include but are not limited to, hypothalamus, choroid plexus, adipose tissues, lung, prostate, ovary, small intestine, bone marrow and peripheral blood mononuclear cells.

5.3.2. THERAPEUTIC USES OF THE OB-R VARIANT POLYNUCLEOTIDE

The OB-R variant polynucleotide may be useful in the treatment of various abnormal obese conditions. By introducing gene sequences into cells, gene therapy can be used to treat conditions in which the cells do not respond to leptin normally due to expression of the OB-R variant. In some instances, the polynucleotide encoding a functional OB-R is intended to replace or act in the place of the functionally deficient OB-R variant gene. Alternatively, abnormal conditions characterized by expression of two copies of the OB-R variant can be treated using the gene therapy techniques described below.

Non-responsiveness to normal levels of leptin is an important cause of obesity. This may result from a functionally defective receptor that does not transduce competent signals upon ligand binding. Recombinant gene therapy vectors, such as viral vectors, may be engineered to express signalling competent forms of OB-R which may be used to augment the non-responsiveness of the naturally occurring OB-R variant. A signalling competent form may be, for example, a protein with the same extracellular domain and transmembrane region, but containing all or part of its normal signal transduction domain, such as that described by Tartaglia et al. (1995, Cell 83:1263-1271). Thus recombinant gene therapy vectors may be used therapeutically for treatment of obesity resulting from expression or activity of the OB-R variant. Accordingly, the invention provides a method of augmenting signal transduction by an endogenous OB-R variant in a cell comprising delivering a DNA molecule encoding a signalling competent form of the OB-R to the cell so that the signalling competent protein is produced in the cell and competes with the endogenous defective OB-R variant for access to molecules in the signalling pathway which does not activate or are not activated by the endogenous natural defective receptor. Additionally, since dimerization of a functional receptor with a defective variant may occur in cells of heterozygous individuals, small molecules may be used to inhibit such pairing, thereby increasing the number of functional dimeric receptors for proper signalling in response to leptin.

In contrast, overexpression of either leptin or a competent OB-R may result in a clinical anorexic-like syndrome due to a loss of appetite or hypermetabolic activity. In such cases, the OB-R variant of the invention may be introduced into cells with functional receptors to cause a decrease in the number of functional receptors or to compete with such receptors for leptin binding.

Expression vectors derived from viruses such as retroviruses, vaccinia virus, adeno-associated virus, herpes viruses, or bovine papilloma virus, may be used for delivery of recombinant functional OB-R into the targeted cell population. Methods which are well known to those skilled in the art can be used to construct recombinant viral vectors containing an OB-R polynucleotide sequence. See, for example, the techniques described in Sambrook et al., 1989, Molecular Cloning A Laboratory Manual, Cold Spring Harbor Laboratory, N.Y. and Ausubel et al., 1989, Current Protocols in Molecular Biology, Greene Publishing Associates and Wiley Interscience, N.Y. Alternatively, recombinant OB-R molecules can be reconstituted into liposomes for delivery to target cells.

Oligonucleotide sequences including anti-sense RNA and DNA molecules and ribozymes that function to inhibit the translation of the OB-R variant mRNA are within the scope of the invention. Anti-sense RNA and DNA molecules act to directly block the translation of mRNA by binding to targeted mRNA and preventing protein translation. In regard to antisense DNA, oligodeoxyribonucleotides derived from the OB-R variant nucleotide sequence at nucleotide #2771 and beyond, are preferred.

Ribozymes are enzymatic RNA molecules capable of catalyzing the specific cleavage of RNA. The mechanism of ribozyme action involves sequence specific hybridization of the ribozyme molecule to complementary target RNA, followed by endonucleolytic cleavage. Within the scope of the invention are engineered hammerhead motif ribozyme molecules that specifically and efficiently catalyze endonucleolytic cleavage of OB-R variant RNA sequences.

Specific ribozyme cleavage sites within any potential RNA target are initially identified by scanning the target molecule for ribozyme cleavage sites which include the following sequences, GUA, GUU and GUC. Once identified, short RNA sequences of between 15 and 20 ribonucleotides corresponding to the region of the target gene containing the cleavage site may be evaluated for predicted structural features such as secondary structure that may render the oligonucleotide sequence unsuitable. The suitability of candidate targets may also be evaluated by testing their accessibility to hybridization with complementary oligonucleotides, using ribonuclease protection assays.

Oligodeoxyribonucleotides can form sequence-specific triple helices by hydrogen bonding to specific complementary sequences in duplexed DNA. Interest in triple helices has focused on the potential biological and therapeutic applications of these structures. Formation of specific triple helices may selectively inhibit the replication and/or gene expression of targeted genes by prohibiting the specific binding of functional trans-acting factors.

Oligonucleotides to be used in triplex helix formation should be single stranded and composed of deoxynucleotides. The base composition of these oligonucleotides must be designed to promote triple helix formation via Hoogsteen base pairing rules, which generally require sizeable stretches of either purines or pyrimidines to be present on one strand of a duplex. Oligonucleotide sequences may be pyrimidine-based, which will result in TAT and CGC triplets across the three associated strands of the resulting triple helix. The pyrimidine-rich oligonucleotides provide base complementarity to a purine-rich region of a single strand of the duplex in a parallel orientation to that strand. In addition, oligonucleotides may be chosen that are purine-rich, for example, containing a stretch of G residues. These oligonucleotides will form a triple helix with a DNA duplex that is rich in GC pairs, in which the majority of the purine residues are located on a single strand of the targeted duplex, resulting in GGC triplets across the three strands in the triplex. Alternatively, the potential sequences that can be targeted for triple helix formation may be increased by creating a so called “switchback” oligonucleotide. Switchback oligonucleotides are synthesized in an alternating 5′-3′, 3′-5′ manner, such that they base pair with first one strand of a duplex and then the other, eliminating the necessity for a sizeable stretch of either purines or pyrimidines to be present on one strand of a duplex.

Both anti-sense RNA and DNA molecules and ribozymes of the invention may be prepared by any method known in the art for the synthesis of RNA molecules. These include techniques for chemically synthesizing oligodeoxyribonucleotides well known in the art such as solid phase phosphoramidite chemical synthesis. Alternatively, RNA molecules may be generated by in vitro and in vivo transcription of DNA sequences encoding the antisense RNA molecule. Such DNA sequences may be incorporated into a wide variety of vectors which incorporate suitable RNA polymerase promoters such as the T7 or SP6 polymerase promoters. Alternatively, antisense cDNA constructs that synthesize antisense RNA constitutively or inducibly, depending on the promoter used, can be introduced stably into cell lines.

Various modifications to the DNA molecules may be introduced as a means of increasing intracellular stability and half-life. Possible modifications include but are not limited to the addition of flanking sequences of ribo- or deoxy- nucleotides to the 5′ and/or 3′ ends of the molecule or the use of phosphorothioate or 2′ O-methyl rather than phosphodiesterase linkages within the oligodeoxyribonucleotide backbone.

5.4. ACTIVATION OF TYROSINE KINASE PATHWAYS IN OBESITY

Many known class I cytokine receptors initiate cell signaling via Janus kinases (JAKs) (Ihle, 1995, Nature 377:591-594; Heldin, 1995, Cell 80:213-223; Kishimoto et al, 1994, Cell 76:253-62; Ziemiecki et al, 1994, Trends Cell. Biol. 4:207-212). JAK1-3 have been shown to bind to conserved sequences termed box1 and box2 (Fukunaga et al., 1991, EMBO J. 10:2855-65; Murakami, 1991, Proc. Natl. Acad. Sci. USA 88:11349-53). Ligand binding induces a homo- or hetero-dimerization of receptor chains which activates, by phosphorylation, the JAKs. The activated JAKs, in turn, phosphorylate members of the STAT family (Heldin, 1995, Cell 80:213-223; Kishimoto et al., Blood 86:1243-54; Darnell et al., 1994, Science 264:1415-21; Zhong et al, 1994, Proc. Natl. Acad. Sci. USA 91:4806-10; Hou et al., 1994, Science 265:1701-6). These phosphorylated STATs ultimately translocate to the nucleus, form transcription complexes, and regulate gene expression. Both box1 and box2 are required for complete signaling in certain systems. (Fukunaga et al., 1991, EMBO J. 10:2855-65; Murakami, 1991, Proc. Natl. Acad. Sci. USA 88:11349-53). The OB-R variant disclosed herein has a typical box1 (from nucleotide #2707-2730) that contains the critical xWxxxPxP amino acid sequence, but it does not contain an obvious box2 nor further downstream sequences that are important for normal receptor activation. Therefore, it is possible to use compounds that activate JAKs to directly activate these pathways for weight regulation without triggering the OB-R.

6. EXAMPLE MOLECULAR CLONING OF AN OB-R VARIANT

A number of cDNA clones were isolated from a human fetal liver cDNA library (Clontech, Palo Alto, Calif.), and the DNA sequences of several of these clones were determined. These clones (designated as Hu-B1.219 #4, #33, #34, #1, #3, #57, #62) contained overlapping sequences, which were then compiled into a contiguous nucleotide sequence (FIGS. 1A-1G). When the deduced amino acid sequence of one such sequence was compared with the sequence of a recently published human OB-R, they were shown to be nearly identical in the extracellular domains with the exception of three amino acids, whereas there existed extensive diversity in their intracellular cytoplasmic domains at the 3′ end. The predicted protein sequence contains two FN III domains, each containing a “WS box”, which are characteristic of genes of the Class I cytokine receptor family. Therefore, the cDNA disclosed herein encodes an OB-R variant.

When various human tissue RNA were probed with a fragment of this OB-R variant by Northern blot analysis, expression of this molecule was detected in heart, placenta, lung, liver, muscle, pancreas, prostate, ovary, small intestine and brain.

Based on the sequence presented in FIGS. 1A-1G, the translation initiation site appears at position #97. The sequence encodes an open reading frame up to and including nucleotide #2784. It is believed that the sequence between nucleotides #2629 and #2682 encodes a transmembrane domain. The complete sequence encodes a protein of 896 amino acids.

The sequence of the OB-R variant is identical to the sequence of human OB-R reported by Tartaglia (1995, Cell 83:1263-1271) in the transmembrane region and a portion of the intracellular domain up to and including nucleotide #2769, then they diverge at nucleotide #2770 and beyond. In addition, the product of this cDNA is substantially shorter in its intracellular domain than the published human OB-R. These two forms of OB-R may derive from a common precursor mRNA by an alternative splicing mechanism. The sequence in this region is consistent with well known splice junctions.

7. DEPOSIT OF MICROORGANISMS

The following organisms were deposited with the American Type Culture Collection (ATCC), 12301 Parklawn Drive, Rockville, Md. 20852.

Strain Designation Accession No. HuB1.219, #1 75885 HuB1.219, #4 75886 HuB1.219, #33 75888 HuB1.219, #34 75889 HuB1.219, #3 75970 HuB1.219, #57 75972 HuB1.219, #62 75974

The present invention is not to be limited in scope by the exemplified embodiments, which are intended as illustrations of individual aspects of the invention. Indeed, various modifications for the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and accompanying drawings. Such modifications are intended to fall within the scope of the appended claims.

All publications cited herein are incorporated by reference in their entirety.

5 2877 base pairs nucleic acid single linear cDNA CDS 1..2871 1 GCG CGC GCG ACG CAG GTG CCC GAG CCC CGG CCC GCG CCC ATC TCT GCC 48 Ala Arg Ala Thr Gln Val Pro Glu Pro Arg Pro Ala Pro Ile Ser Ala 1 5 10 15 TTC GGT CGA GTT GGA CCC CCG GAT CAA GGT GTA CTT CTC TGA AGT AAG 96 Phe Gly Arg Val Gly Pro Pro Asp Gln Gly Val Leu Leu * Ser Lys 20 25 30 ATG ATT TGT CAA AAA TTC TGT GTG GTT TTG TTA CAT TGG GAA TTT ATT 144 Met Ile Cys Gln Lys Phe Cys Val Val Leu Leu His Trp Glu Phe Ile 35 40 45 TAT GTG ATA ACT GCG TTT AAC TTG TCA TAT CCA ATT ACT CCT TGG AGA 192 Tyr Val Ile Thr Ala Phe Asn Leu Ser Tyr Pro Ile Thr Pro Trp Arg 50 55 60 TTT AAG TTG TCT TGC ATG CCA CCA AAT TCA ACC TAT GAC TAC TTC CTT 240 Phe Lys Leu Ser Cys Met Pro Pro Asn Ser Thr Tyr Asp Tyr Phe Leu 65 70 75 80 TTG CCT GCT GGA CTC TCA AAG AAT ACT TCA AAT TCG AAT GGA CAT TAT 288 Leu Pro Ala Gly Leu Ser Lys Asn Thr Ser Asn Ser Asn Gly His Tyr 85 90 95 GAG ACA GCT GTT GAA CCT AAG TTT AAT TCA AGT GGT ACT CAC TTT TCT 336 Glu Thr Ala Val Glu Pro Lys Phe Asn Ser Ser Gly Thr His Phe Ser 100 105 110 AAC TTA TCC AAA GCA ACT TTC CAC TGT TGC TTT CGG AGT GAG CAA GAT 384 Asn Leu Ser Lys Ala Thr Phe His Cys Cys Phe Arg Ser Glu Gln Asp 115 120 125 AGA AAC TGC TCC TTA TGT GCA GAC AAC ATT GAA GGA AGG ACA TTT GTT 432 Arg Asn Cys Ser Leu Cys Ala Asp Asn Ile Glu Gly Arg Thr Phe Val 130 135 140 TCA ACA GTA AAT TCT TTA GTT TTT CAA CAA ATA GAT GCA AAC TGG AAC 480 Ser Thr Val Asn Ser Leu Val Phe Gln Gln Ile Asp Ala Asn Trp Asn 145 150 155 160 ATA CAG TGC TGG CTA AAA GGA GAC TTA AAA TTA TTC ATC TGT TAT GTG 528 Ile Gln Cys Trp Leu Lys Gly Asp Leu Lys Leu Phe Ile Cys Tyr Val 165 170 175 GAG TCA TTA TTT AAG AAT CTA TTC AGG AAT TAT AAC TAT AAG GTC CAT 576 Glu Ser Leu Phe Lys Asn Leu Phe Arg Asn Tyr Asn Tyr Lys Val His 180 185 190 CTT TTA TAT GTT CTG CCT GAA GTG TTA GAA GAT TCA CCT CTG GTT CCC 624 Leu Leu Tyr Val Leu Pro Glu Val Leu Glu Asp Ser Pro Leu Val Pro 195 200 205 CAA AAA GGC AGT TTT CAG ATG GTT CAC TGC AAT TGC AGT GTT CAT GAA 672 Gln Lys Gly Ser Phe Gln Met Val His Cys Asn Cys Ser Val His Glu 210 215 220 TGT TGT GAA TGT CTT GTG CCT GTG CCA ACA GCC AAA CTC AAC GAC ACT 720 Cys Cys Glu Cys Leu Val Pro Val Pro Thr Ala Lys Leu Asn Asp Thr 225 230 235 240 CTC CTT ATG TGT TTG AAA ATC ACA TCT GGT GGA GTA ATT TTC CGG TCA 768 Leu Leu Met Cys Leu Lys Ile Thr Ser Gly Gly Val Ile Phe Arg Ser 245 250 255 CCT CTA ATG TCA GTT CAG CCA ATA AAT ATG GTG AAG CCT GAT CCA CCA 816 Pro Leu Met Ser Val Gln Pro Ile Asn Met Val Lys Pro Asp Pro Pro 260 265 270 TTA GGT TTG CAT ATG GAA ATC ACA GAT GAT GGT AAT TTA AAG ATT TCT 864 Leu Gly Leu His Met Glu Ile Thr Asp Asp Gly Asn Leu Lys Ile Ser 275 280 285 TGG TCC AGC CCA CCA TTG GTA CCA TTT CCA CTT CAA TAT CAA GTG AAA 912 Trp Ser Ser Pro Pro Leu Val Pro Phe Pro Leu Gln Tyr Gln Val Lys 290 295 300 TAT TCA GAG AAT TCT ACA ACA GTT ATC AGA GAA GCT GAC AAG ATT GTC 960 Tyr Ser Glu Asn Ser Thr Thr Val Ile Arg Glu Ala Asp Lys Ile Val 305 310 315 320 TCA GCT ACA TCC CTG CTA GTA GAC AGT ATA CTT CCT GGG TCT TCG TAT 1008 Ser Ala Thr Ser Leu Leu Val Asp Ser Ile Leu Pro Gly Ser Ser Tyr 325 330 335 GAG GTT CAG GTG AGG GGC AAG AGA CTG GAT GGC CCA GGA ATC TGG AGT 1056 Glu Val Gln Val Arg Gly Lys Arg Leu Asp Gly Pro Gly Ile Trp Ser 340 345 350 GAC TGG AGT ACT CCT CGT GTC TTT ACC ACA CAA GAT GTC ATA TAC TTT 1104 Asp Trp Ser Thr Pro Arg Val Phe Thr Thr Gln Asp Val Ile Tyr Phe 355 360 365 CCA CCT AAA ATT CTG ACA AGT GTT GGG TCT AAT GTT TCT TTT CAC TGC 1152 Pro Pro Lys Ile Leu Thr Ser Val Gly Ser Asn Val Ser Phe His Cys 370 375 380 ATC TAT AAG AAG GAA AAC AAG ATT GTT CCC TCA AAA GAG ATT GTT TGG 1200 Ile Tyr Lys Lys Glu Asn Lys Ile Val Pro Ser Lys Glu Ile Val Trp 385 390 395 400 TGG ATG AAT TTA GCT GAG AAA ATT CCT CAA AGC CAG TAT GAT GTT GTG 1248 Trp Met Asn Leu Ala Glu Lys Ile Pro Gln Ser Gln Tyr Asp Val Val 405 410 415 AGT GAT CAT GTT AGC AAA GTT ACT TTT TTC AAT CTG AAT GAA ACC AAA 1296 Ser Asp His Val Ser Lys Val Thr Phe Phe Asn Leu Asn Glu Thr Lys 420 425 430 CCT CGA GGA AAG TTT ACC TAT GAT GCA GTG TAC TGC TGC AAT GAA CAT 1344 Pro Arg Gly Lys Phe Thr Tyr Asp Ala Val Tyr Cys Cys Asn Glu His 435 440 445 GAA TGC CAT CAT CGC TAT GCT GAA TTA TAT GTG ATT GAT GTC AAT ATC 1392 Glu Cys His His Arg Tyr Ala Glu Leu Tyr Val Ile Asp Val Asn Ile 450 455 460 AAT ATC TCA TGT GAA ACT GAT GGG TAC TTA ACT AAA ATG ACT TGC AGA 1440 Asn Ile Ser Cys Glu Thr Asp Gly Tyr Leu Thr Lys Met Thr Cys Arg 465 470 475 480 TGG TCA ACC AGT ACA ATC CAG TCA CTT GCG GAA AGC ACT TTG CAA TTG 1488 Trp Ser Thr Ser Thr Ile Gln Ser Leu Ala Glu Ser Thr Leu Gln Leu 485 490 495 AGG TAT CAT AGG AGC AGC CTT TAC TGT TCT GAT ATT CCA TCT ATT CAT 1536 Arg Tyr His Arg Ser Ser Leu Tyr Cys Ser Asp Ile Pro Ser Ile His 500 505 510 CCC ATA TCT GAG CCC AAA GAT TGC TAT TTG CAG AGT GAT GGT TTT TAT 1584 Pro Ile Ser Glu Pro Lys Asp Cys Tyr Leu Gln Ser Asp Gly Phe Tyr 515 520 525 GAA TGC ATT TTC CAG CCA ATC TTC CTA TTA TCT GGC TAC ACA ATG TGG 1632 Glu Cys Ile Phe Gln Pro Ile Phe Leu Leu Ser Gly Tyr Thr Met Trp 530 535 540 ATT AGG ATC AAT CAC TCT CTA GGT TCA CTT GAC TCT CCA CCA ACA TGT 1680 Ile Arg Ile Asn His Ser Leu Gly Ser Leu Asp Ser Pro Pro Thr Cys 545 550 555 560 GTC CTT CCT GAT TCT GTG GTG AAG CCA CTG CCT CCA TCC AGT GTG AAA 1728 Val Leu Pro Asp Ser Val Val Lys Pro Leu Pro Pro Ser Ser Val Lys 565 570 575 CGA GAA ATT ACT ATA AAC ATT GGA TTA TTG AAA ATA TCT TGG GAA AAG 1776 Arg Glu Ile Thr Ile Asn Ile Gly Leu Leu Lys Ile Ser Trp Glu Lys 580 585 590 CCA GTC TTT CCA GAG AAT AAC CTT CAA TTC CAG ATT CGC TAT GGT TTA 1824 Pro Val Phe Pro Glu Asn Asn Leu Gln Phe Gln Ile Arg Tyr Gly Leu 595 600 605 AGT GGA AAA GAA GTA CAA TGG AAG ATG TAT GAG GTT TAT GAT CGA AAA 1872 Ser Gly Lys Glu Val Gln Trp Lys Met Tyr Glu Val Tyr Asp Arg Lys 610 615 620 TCA AAA TCT GTC AGT CTC CCA GTT CCA GAC TTG TGT GCA GTC TAT GCT 1920 Ser Lys Ser Val Ser Leu Pro Val Pro Asp Leu Cys Ala Val Tyr Ala 625 630 635 640 GTT CAG GTG CGC TGT AAG AGG CTA GAT GGA CTG GGA TAT TGG AGT AAT 1968 Val Gln Val Arg Cys Lys Arg Leu Asp Gly Leu Gly Tyr Trp Ser Asn 645 650 655 TGG AGC AAT CCA GCC TAC ACA GTT GTC ATG GAT ATA AAA GTT CCT ATG 2016 Trp Ser Asn Pro Ala Tyr Thr Val Val Met Asp Ile Lys Val Pro Met 660 665 670 AGA GGA CCT GAA TTT TGG AGA ATA ATT AAT GGA GAT ACT ATG AAA AAG 2064 Arg Gly Pro Glu Phe Trp Arg Ile Ile Asn Gly Asp Thr Met Lys Lys 675 680 685 GAG AAA AAT GTC ACT TTA CTT TGG AAG CCC CTG ATG AAA AAT GAC TCA 2112 Glu Lys Asn Val Thr Leu Leu Trp Lys Pro Leu Met Lys Asn Asp Ser 690 695 700 TTG TGC AGT GTT CAG AGA TAT GTG ATA AAC CAT CAT ACT TCC TGC AAT 2160 Leu Cys Ser Val Gln Arg Tyr Val Ile Asn His His Thr Ser Cys Asn 705 710 715 720 GGA ACA TGG TCA GAA GAT GTG GGA AAT CAC ACG AAA TTC ACT TTC CTG 2208 Gly Thr Trp Ser Glu Asp Val Gly Asn His Thr Lys Phe Thr Phe Leu 725 730 735 TGG ACA GAG CAA GCA CAT ACT GTT ACG GTT CTG GCC ATC AAT TCA ATT 2256 Trp Thr Glu Gln Ala His Thr Val Thr Val Leu Ala Ile Asn Ser Ile 740 745 750 GGT GCT TCT GTT GCA AAT TTT AAT TTA ACC TTT TCA TGG CCT ATG AGC 2304 Gly Ala Ser Val Ala Asn Phe Asn Leu Thr Phe Ser Trp Pro Met Ser 755 760 765 AAA GTA AAT ATC GTG CAG TCA CTC AGT GCT TAT CCT TTA AAC AGC AGT 2352 Lys Val Asn Ile Val Gln Ser Leu Ser Ala Tyr Pro Leu Asn Ser Ser 770 775 780 TGT GTG ATT GTT TCC TGG ATA CTA TCA CCC AGT GAT TAC AAG CTA ATG 2400 Cys Val Ile Val Ser Trp Ile Leu Ser Pro Ser Asp Tyr Lys Leu Met 785 790 795 800 TAT TTT ATT ATT GAG TGG AAA AAT CTT AAT GAA GAT GGT GAA ATA AAA 2448 Tyr Phe Ile Ile Glu Trp Lys Asn Leu Asn Glu Asp Gly Glu Ile Lys 805 810 815 TGG CTT AGA ATC TCT TCA TCT GTT AAG AAG TAT TAT ATC CAT GAT CAT 2496 Trp Leu Arg Ile Ser Ser Ser Val Lys Lys Tyr Tyr Ile His Asp His 820 825 830 TTT ATC CCC ATT GAG AAG TAC CAG TTC AGT CTT TAC CCA ATA TTT ATG 2544 Phe Ile Pro Ile Glu Lys Tyr Gln Phe Ser Leu Tyr Pro Ile Phe Met 835 840 845 GAA GGA GTG GGA AAA CCA AAG ATA ATT AAT AGT TTC ACT CAA GAT GAT 2592 Glu Gly Val Gly Lys Pro Lys Ile Ile Asn Ser Phe Thr Gln Asp Asp 850 855 860 ATT GAA AAA CAC CAG AGT GAT GCA GGT TTA TAT GTA ATT GTG CCA GTA 2640 Ile Glu Lys His Gln Ser Asp Ala Gly Leu Tyr Val Ile Val Pro Val 865 870 875 880 ATT ATT TCC TCT TCC ATC TTA TTG CTT GGA ACA TTA TTA ATA TCA CAC 2688 Ile Ile Ser Ser Ser Ile Leu Leu Leu Gly Thr Leu Leu Ile Ser His 885 890 895 CAA AGA ATG AAA AAG CTA TTT TGG GAA GAT GTT CCG AAC CCC AAG AAT 2736 Gln Arg Met Lys Lys Leu Phe Trp Glu Asp Val Pro Asn Pro Lys Asn 900 905 910 TGT TCC TGG GCA CAA GGA CTT AAT TTT CAG AAG AGA ACG GAC ATT CTT 2784 Cys Ser Trp Ala Gln Gly Leu Asn Phe Gln Lys Arg Thr Asp Ile Leu 915 920 925 TGA AGT CTA ATC ATG ATC ACT ACA GAT GAA CCC AAT GTG CCA ACT TCC 2832 * Ser Leu Ile Met Ile Thr Thr Asp Glu Pro Asn Val Pro Thr Ser 930 935 940 945 CAA CAG TCT ATA GAG TAT TAG AAG ATT TTT ACA TTC TGA AGA AGG 2877 Glu Glu Ser Ile Glu Tyr * Lys Ile Glu Thr Phe * Arg Arg 29 amino acids amino acid linear protein 2 Ala Arg Ala Thr Gln Val Pro Glu Pro Arg Pro Ala Pro Ile Ser Ala 1 5 10 15 Phe Gly Arg Val Gly Pro Pro Asp Gln Gly Val Leu Leu 20 25 898 amino acids amino acid linear protein 3 Ser Lys Met Ile Cys Gln Lys Phe Cys Val Val Leu Leu His Trp Glu 1 5 10 15 Phe Ile Tyr Val Ile Thr Ala Phe Asn Leu Ser Tyr Pro Ile Thr Pro 20 25 30 Trp Arg Phe Lys Leu Ser Cys Met Pro Pro Asn Ser Thr Tyr Asp Tyr 35 40 45 Phe Leu Leu Pro Ala Gly Leu Ser Lys Asn Thr Ser Asn Ser Asn Gly 50 55 60 His Tyr Glu Thr Ala Val Glu Pro Lys Phe Asn Ser Ser Gly Thr His 65 70 75 80 Phe Ser Asn Leu Ser Lys Ala Thr Phe His Cys Cys Phe Arg Ser Glu 85 90 95 Gln Asp Arg Asn Cys Ser Leu Cys Ala Asp Asn Ile Glu Gly Arg Thr 100 105 110 Phe Val Ser Thr Val Asn Ser Leu Val Phe Gln Gln Ile Asp Ala Asn 115 120 125 Trp Asn Ile Gln Cys Trp Leu Lys Gly Asp Leu Lys Leu Phe Ile Cys 130 135 140 Tyr Val Glu Ser Leu Phe Lys Asn Leu Phe Arg Asn Tyr Asn Tyr Lys 145 150 155 160 Val His Leu Leu Tyr Val Leu Pro Glu Val Leu Glu Asp Ser Pro Leu 165 170 175 Val Pro Gln Lys Gly Ser Phe Gln Met Val His Cys Asn Cys Ser Val 180 185 190 His Glu Cys Cys Glu Cys Leu Val Pro Val Pro Thr Ala Lys Leu Asn 195 200 205 Asp Thr Leu Leu Met Cys Leu Lys Ile Thr Ser Gly Gly Val Ile Phe 210 215 220 Arg Ser Pro Leu Met Ser Val Gln Pro Ile Asn Met Val Lys Pro Asp 225 230 235 240 Pro Pro Leu Gly Leu His Met Glu Ile Thr Asp Asp Gly Asn Leu Lys 245 250 255 Ile Ser Trp Ser Ser Pro Pro Leu Val Pro Phe Pro Leu Gln Tyr Gln 260 265 270 Val Lys Tyr Ser Glu Asn Ser Thr Thr Val Ile Arg Glu Ala Asp Lys 275 280 285 Ile Val Ser Ala Thr Ser Leu Leu Val Asp Ser Ile Leu Pro Gly Ser 290 295 300 Ser Tyr Glu Val Gln Val Arg Gly Lys Arg Leu Asp Gly Pro Gly Ile 305 310 315 320 Trp Ser Asp Trp Ser Thr Pro Arg Val Phe Thr Thr Gln Asp Val Ile 325 330 335 Tyr Phe Pro Pro Lys Ile Leu Thr Ser Val Gly Ser Asn Val Ser Phe 340 345 350 His Cys Ile Tyr Lys Lys Glu Asn Lys Ile Val Pro Ser Lys Glu Ile 355 360 365 Val Trp Trp Met Asn Leu Ala Glu Lys Ile Pro Gln Ser Gln Tyr Asp 370 375 380 Val Val Ser Asp His Val Ser Lys Val Thr Phe Phe Asn Leu Asn Glu 385 390 395 400 Thr Lys Pro Arg Gly Lys Phe Thr Tyr Asp Ala Val Tyr Cys Cys Asn 405 410 415 Glu His Glu Cys His His Arg Tyr Ala Glu Leu Tyr Val Ile Asp Val 420 425 430 Asn Ile Asn Ile Ser Cys Glu Thr Asp Gly Tyr Leu Thr Lys Met Thr 435 440 445 Cys Arg Trp Ser Thr Ser Thr Ile Gln Ser Leu Ala Glu Ser Thr Leu 450 455 460 Gln Leu Arg Tyr His Arg Ser Ser Leu Tyr Cys Ser Asp Ile Pro Ser 465 470 475 480 Ile His Pro Ile Ser Glu Pro Lys Asp Cys Tyr Leu Gln Ser Asp Gly 485 490 495 Phe Tyr Glu Cys Ile Phe Gln Pro Ile Phe Leu Leu Ser Gly Tyr Thr 500 505 510 Met Trp Ile Arg Ile Asn His Ser Leu Gly Ser Leu Asp Ser Pro Pro 515 520 525 Thr Cys Val Leu Pro Asp Ser Val Val Lys Pro Leu Pro Pro Ser Ser 530 535 540 Val Lys Arg Glu Ile Thr Ile Asn Ile Gly Leu Leu Lys Ile Ser Trp 545 550 555 560 Glu Lys Pro Val Phe Pro Glu Asn Asn Leu Gln Phe Gln Ile Arg Tyr 565 570 575 Gly Leu Ser Gly Lys Glu Val Gln Trp Lys Met Tyr Glu Val Tyr Asp 580 585 590 Arg Lys Ser Lys Ser Val Ser Leu Pro Val Pro Asp Leu Cys Ala Val 595 600 605 Tyr Ala Val Gln Val Arg Cys Lys Arg Leu Asp Gly Leu Gly Tyr Trp 610 615 620 Ser Asn Trp Ser Asn Pro Ala Tyr Thr Val Val Met Asp Ile Lys Val 625 630 635 640 Pro Met Arg Gly Pro Glu Phe Trp Arg Ile Ile Asn Gly Asp Thr Met 645 650 655 Lys Lys Glu Lys Asn Val Thr Leu Leu Trp Lys Pro Leu Met Lys Asn 660 665 670 Asp Ser Leu Cys Ser Val Gln Arg Tyr Val Ile Asn His His Thr Ser 675 680 685 Cys Asn Gly Thr Trp Ser Glu Asp Val Gly Asn His Thr Lys Phe Thr 690 695 700 Phe Leu Trp Thr Glu Gln Ala His Thr Val Thr Val Leu Ala Ile Asn 705 710 715 720 Ser Ile Gly Ala Ser Val Ala Asn Phe Asn Leu Thr Phe Ser Trp Pro 725 730 735 Met Ser Lys Val Asn Ile Val Gln Ser Leu Ser Ala Tyr Pro Leu Asn 740 745 750 Ser Ser Cys Val Ile Val Ser Trp Ile Leu Ser Pro Ser Asp Tyr Lys 755 760 765 Leu Met Tyr Phe Ile Ile Glu Trp Lys Asn Leu Asn Glu Asp Gly Glu 770 775 780 Ile Lys Trp Leu Arg Ile Ser Ser Ser Val Lys Lys Tyr Tyr Ile His 785 790 795 800 Asp His Phe Ile Pro Ile Glu Lys Tyr Gln Phe Ser Leu Tyr Pro Ile 805 810 815 Phe Met Glu Gly Val Gly Lys Pro Lys Ile Ile Asn Ser Phe Thr Gln 820 825 830 Asp Asp Ile Glu Lys His Gln Ser Asp Ala Gly Leu Tyr Val Ile Val 835 840 845 Pro Val Ile Ile Ser Ser Ser Ile Leu Leu Leu Gly Thr Leu Leu Ile 850 855 860 Ser His Gln Arg Met Lys Lys Leu Phe Trp Glu Asp Val Pro Asn Pro 865 870 875 880 Lys Asn Cys Ser Trp Ala Gln Gly Pro Asn Phe Gln Lys Arg Thr Asp 885 890 895 Ile Leu 21 amino acids amino acid linear protein 4 Ser Leu Ile Met Ile Thr Thr Asp Glu Pro Asn Val Pro Thr Ser Gln Gln 1 5 10 15 Ser Ile Glu Tyr 20 5 amino acids amino acid linear protein 5 Lys Ile Phe Thr Phe 1 5 

What is claimed is:
 1. A method for detecting a nucleic acid encoding a leptin receptor variant in a cell, comprising: (a) contacting a nucleic acid molecule derived from the cell with a polynucleotide selected from the group consisting of (i) nucleotides #2770 through #2877 of SEQ ID NO:1; (ii) the complement of the polynucleotide of (i); (iii) a portion of the polynucleotide of (i) that hybridizes to a nucleic acid comprising the polynucleotide of (ii) under stringent conditions; and (iv) a portion of the polynucleotide of (ii) that hybridizes to a nucleic acid comprising the polynucleotide of (i) under stringent conditions; wherein the stringent conditions recited in (iii) and (iv) are selected from the group consisting of: (i) washing at 50° C. with 0.015 M NaCl, 0.0015 M sodium citrate and 0.1% SDS; and (ii) washing at 42° C. in 0.2×SSC and 0.1% SDS; and (b) detecting hybridization of the polynucleotide with the nucleic acid molecule.
 2. The method of claim 1 in which the polynucleotide comprises a nucleotide sequence as shown in SEQ ID NO:1 between #2770 and #2784 or a portion thereof, or its complementary sequence or a portion thereof.
 3. The method of claim 1 in which the nucleic acid molecule is ribonucleic acid.
 4. The method of claim 3 in which the ribonucleic acid is first extracted from the cell.
 5. The method of claim 1 in which the nucleic acid molecule is deoxyribonucleic acid.
 6. The method of claim 5 in which the deoxyribonucleic acid is first extracted from the cell.
 7. The method of claim 1 in which the hybridization is detected by an in situ hybridization method.
 8. The method of claim 1 in which the hybridization is detected by Northern blot analysis method.
 9. The method claim 1 in which the polynucleotide of step (a) is used as a primer in an amplification reaction.
 10. The method of claim 9 in which the amplification reaction is the polymerase chain reaction.
 11. The method of claim 1 in which the cell is obtained from hypothalamus.
 12. The method of claim 1 in which the cell is obtained from choroid plexus.
 13. The method of claim 1 in which the cell is obtained from adipose tissue.
 14. The method of claim 1 in which the cell is obtained from lung.
 15. The method of claim 1 in which the cell is obtained from prostate.
 16. The method of claim 1 in which the cell is obtained from ovary.
 17. The method of claim 1 in which the cell is obtained from small intestine.
 18. The method of claim 1 in which the cell is obtained from bone marrow.
 19. The method of claim 1 in which the cell is obtained from peripheral blood. 